Engineer's Corner

4:50 pm

Thu November 21, 2013

We've talked in the past about skywave propagation, but it's cool when you heard about real-world examples of it. Recently I've gotten several emails from "DX'ers" (Distant Reception enthusiasts) in Europe saying they've been able to hear Latino Public Radio on 1290AM all the way across the Atlantic!

We have put a temporary setup in place with a donated 30 watt transmitter on loan (with the antenna array's gain factor of 2.1, it's really more like 63 watts of Effective Radiated Power), and a special radio that's tuned to 102.7FM (there's a high-gain FM antenna on the rooftop tower) and puts out the composite signal directly into the new transmitter. This effectively makes 91.5 into a "repeater" of 102.7FM.

Engineer's Corner

12:39 pm

Thu October 17, 2013

UPDATE 01/21: Multiple letters sent with no response, and the pirate's still broadcasting. A letter has been mailed to the FCC's Enforcement Bureau. If you are an RIPR listener to 102.7 and you have experienced interference due to this pirate, you can submit your own letter to the FCC as well.

UPDATE 12/19: The pirate has been found! Well, we're pretty sure we have found the pirate. Using a directional antenna and a signal meter, we triangulated the position to a house a few blocks from the Locust Grove Cemetery in South Providence.

A letter of notification of interference to RIPR was mailed to this address several weeks ago, but apparently this pirate doesn't care as there's still an illegal broadcast on 102.9 from this location.

UPDATE 11/5: Thanks to a fellow engineer who informed me there is a pirate broadcasting on 102.9FM and that is likely the source of the interference people have reported (see below). Quite possibly the atmospheric changes made it worse, but the bulk of the problem is likely the pirate.

Engineer's Corner

3:00 am

Tue October 15, 2013

As all RIPR fans know, we are an NPR member station. That means we get a lot of our programming from NPR, the BBC, and other providers, via our satellite dish. The dish is medium-sized as dishes go, but it’s pretty big in real terms: 3.7 meters (12ft) in diameter. There’s quite literally nowhere to fit a dish that large at our studios in 1 Union Station, so instead it was installed out at our 1290AM transmitter site in North Providence (we still own 1290, but we lease it to Latino Public R

When you’re a broadcast engineer, you get used to receiving calls at odd hours proclaiming things that tend to fall outside the bounds of “normal.” It’s just the nature of the job. But even your intrepid engineer can be surprised sometimes. Friday morning, August 23rd, was one of those times.

That morning I got a call informing me that WCVY, our 91.5FM signal for much of Kent County, was off the air.

Engineer's Corner

9:23 am

Wed August 14, 2013

Air conditioning. Cool heaven for those who have it, blazing hell for those who don't. It didn't used to be terribly common in broadcast engineering, but it's become moreso in the last ten years. The reason is that, more and more, audio processors, RDS encoders, audio encoders/decoders, studio/transmitter links, remote control systems, and even the transmitters themselves, have all become increasingly "computer-like" with IC's, hard disk drives, power supplies, electrolytic capacitors and the like. All things that fail quickly when operated in temperatures above 80 or so, and the warmer it gets, the faster they fail!

Engineer's Corner

7:56 pm

Wed July 24, 2013

Most people have heard of the "Three Mile Island" nuclear power plant accident of 1979. But it's famous among engineers for being a "normal accident", in that there wasn't any one thing that nearly caused a meltdown of catastrophic proportions...it was a series of little things inside a highly complex system that all happened as part of "normal" operations. None of which, by themselves, was terribly problematic. But they all happened at once, and that was a problem.

Engineer's Corner

1:26 pm

Fri July 12, 2013

BOO! This time on the Engineer’s Corner, we’ll talk about PHANTOM POWER. Usually not as ghoulish as one might expect, phantom power has to do with microphones. Specifically, some microphones have active circuitry inside them. That means they need power to operate, but it’s unwieldy to run a separate power cord and audio microphone cable. So a phantom circuit is used to provide DC power on the same three wires (positive/hot, negative/cold, and ground) out to the microphone that the audio from the mic also uses.

A phantom circuit is one of those nifty things in electronics that looks, to the layman, like it can’t possibly work...but it does anyway.

It has to do with our satellite downlink from NPR. We have a hefty 13-foot-diameter satellite dish, located in North Providence; there's no room for it at One Union Station! It points to "Galaxy 16," a telecommunications satellite in "geostationary" orbit that all NPR stations use.

"Geostationary," also popularly referred to as "geosynchronous," means that the satellite orbits the Earth in sync with the Earth's rotation...about 6800 MPH. That's pretty fast, but the key is that it's the SAME speed for both. So from our perspective here on Earth, the satellite just floats there, not moving, over 22,000 miles up in the sky! In Galaxy 16's case, the satellite is at 99.0 degrees west longitude, meaning it's fixed above a point on the equator over the Pacific Ocean, about 500 miles west of the Galapagos Islands (near Ecuador).

In general, geostationary orbits work great for communications satellites like for NPR, but there's a catch: twice a year there are a few days when, the Sun appears to pass right "behind" the satellite for a few minutes each day. The Sun puts out so much energy on ALL frequencies that it completely swamps the satellite's own signal, so we lose all NPR, BBC and other satellite programming.